Cauliflower response to gypsum on a coarse-textured soil: Relationship between tipburn and leaf nutrient distribution

A field study was conducted on a Hubbard loamy sand low in exchangeable Ca to determine the influence of gypsum on cauliflower (Brassica oleracea Botrytis cv. ‘Snow Crown’) nutrition, yield, and quality. Four rates of gypsum (0, 560, 1120, and 2240 kg/ha) were incorporated before planting. Extractable soil Ca and S increased linearly with increasing gypsum rate. Despite increases in tissue Ca with gypsum application, tipburn of immature leaves was apparent in all treatments. Gypsum had no effect on final yield, curd size, or tipburn severity. Relative levels of Ca, K, P, and Mg were determined in frozen-hydrated and freeze-dried leaf tissue from tipburned and non-tipburned leaves using a scanning electron microscope with x-ray microanalysis. Distribution of these elements was also determined in digested leaf tissue using an ICP spectrometer. Results of x-ray microanalysis indicated that Ca was relatively low and K and P relatively high near necrotic tip areas. No consistent differences in Ca, K, and P distribution were apparent in non-tipburned leaves. Magnesium appeared to be unrelated to the tipburn disorder. Distribution of leaf Ca was qualitatively similar when ICP and x-ray microanalysis techniques were compared. Although Ca nutrition may be involved in tipburn, soil applied gypsum as a Ca source did not alleviate the symptoms.